Induction heating apparatus and method

ABSTRACT

A desirable relative relationship between an inductor and a workpiece surface is measured by directing an air jet toward the workpiece surface from an outlet of an air delivery means stationarily positioned adjacent the inductor. Back pressure in the air delivery means is sensed to indicate the existence of desired relative relationship between the inductor and workpiece surface.

te States atent [1 1 DelPaggio 3,757,072 Sept. 4, 1973 INDUCTION HEATING APPARATUS AND METHOD Inventor: Anthony F. DelPaggio, Parma, Ohio Park Ohio Industries, Inc., Cleveland, Ohio Filed: Aug. 10, 1972 Appl. No; 279,700

Assignee:

US. Cl 219/1041, 219/1057, 219/1073, 219/1075, 219/1079, 266/5 E Int. Cl. H05b 5/02 Field of Search 219/10.41, 10.57, 219/1067, 10.69, 10.73, 10.75, 10.77, 10.79; 266/4 E, 5 E

References Cited UNITED STATES PATENTS 4/1969 Seulen et a1. 219/1057 X Primary Examiner-Joseph V. Truhe Assistant ExaminerB. A. Reynolds Attorney-James H. Tilberry, Robert V. Vickers et a1.

[5 7] ABSTRACT A desirable relative relationship between an inductor and a workpiece surface is measured by directing an air jet toward the workpiece surface from an outlet of an air delivery means stationarily positioned adjacent the inductor. Back pressure in the air delivery means is sensed to indicate the existence of desired relative relationship between the inductor and workpiece surface.

13 Claims, 5 Drawing Figures I TRANSFORMER PATENTED SHEET 1 [IF 4 [TRANSFORMER FIG! ACCUMULATOR PAIENIEDSEP 4197a SHEET 2 BF 4 PATENTED 41973 SHEET 3 BF 4 FIG,.

MAIR LINE PATENTED 41975 3.757. 072

sum u 0F 4 Vii INDUCTION HEATING APPARATUS AND METHOD BACKGROUND OF THE INVENTION This application relates to the art of induction heating, and more particularly to inductive heating and quench hardening of metal members. The invention is particularly applicable to inductive heating and quench hardening of shafts or shaft-like members having an outwardly extending flange at one end portion thereof. However, it will be appreciated that the invention has broader applications and may be used for inductively heating other metal members.

It is common to inductively harden axleshafts or the like having an elongated generally cylindrical shaft portion and an outwardly extending flange at one end of the shaft portion. The flange has a surface facing the shaft portion, and a fillet extends between the surface and the shaft portion. In order to inductively heat and quench harden the fillet, it is necessary to induce currents in the flange as well as the shaft portion. In order to make the induced current in the flange of an optimum value, it is necessary that the flange be accurately positioned closely adjacent to the inductor.

In induction heating, the use of standard gaging practice is impractical. The intense magnetic field in the vicinity of the inductor combined with the heat, quench water and scale create an environment which makes gaging, using conventional means, an impossible task.

In previous arrangements of the type described, it is common to use a tubular inductor coil formed into a circle and having an open center through which the shaft portion extends. Either the axleshaft or the inductor is moved until the flange surface is positioned closely adjacent the inductor.

Variations in thickness of the flange make it difficult to accurately position the flange surface at an optimum distance from the inductor. Limit switches connected with the mechanism for moving either the inductor or the axleshaft do not account for variations in flange thickness. Thus, setting of such limit switches for an average thickness of various flanges will achieve optimum inductive currents in the flange only for those flanges having that average thickness. If the flange is slightly thicker, the inductor may be damaged because the flange surface may contact the inductor before the limit switch operates. If the flange is somewhat thinner than usual, the flange will be positioned too far away from the inductor for achieving optimum induced current flow in the flange for hardening the fillet.

It is also known to use fixed stops for positioning of the flange surface relative to the inductor. The same problems encountered with limit switches apply to the use of fixed stops.

It would be desirable to have an accurate way of measuring the distance between the inductor and the flange surface for properly positioning the flange relative to the inductor regardless of variations in flange thickness, or for indicating situations when the flange thickness is above or below a desirable value.

SUMMARY OF THE INVENTION An induction heating apparatus of the type described includes a measuring means for measuring a desirable relative relationship between the inductor and the flange surface.

In accordance with one arrangemencthe measuring means includes air delivery means having an outlet stationarily positioned adjacent the inductor for directing an air jet toward the workpiece surface. Sensing means is provided for sensing back pressure in the air delivery means to indicate existence of the desired relative relationship.

In one arrangement, the inductor has a hollow interior and a peripheral wall. The air delivery means includes a nozzle having at least a portion thereof projecting through the peripheral wall of the inductor into the hollow interior thereof. With this arrangement, circulation of fluid coolant through the hollow interior of the inductor also contacts and cools the nozzle.

The improved measuring and sensing arrangement constructed in accordance with the present invention may be used for indicating any of several different relative relationships between the inductor and a workpiece surface. In one arrangement, the measuring and sensing device may be used to indicate whether the thickness of an axleshaft flange is beyond its desirable limits. For example, conventional limit switch arrangernents may be set for positioning the surface of the flange closely adjacent the inductor. If the flange is too thick, a higher back pressure, outside of a predetermined range, will be indicated and the workpiece can be rejected without heat treating as being beyond tolerance. If the axleshaft flange is not thick enough, the back pressure indicated will be lower than a predetermined range and the workpiece can be rejected without heat treating as being beyond tolerance.

In another arrangement, the measuring and sensing device may be used for accurately positioning the surface of a workpiece closely adjacent the inductor. When the surface of the workpiece is closely adjacent the inductor, the back pressure in the air delivery means may be used for automatically stopping relative movement between the inductor and workpiece so that heat treatment can be started.

It is a principal object of the present invention to provide an improved apparatus and method for inductively heating workpieces.

It is another object of the present invention to provide such an apparatus and method with means for indicating a desirable relative relationship between an inductor and a workpiece surface.

It is a further object of the present invention to provide an improved arrangement for measuring and sensing the position of a workpiece surface relative to an inductor.

It is also an object of the present invention to provide I an arrangement for cooling an air delivery means mounted on an inductor.

BRIEF DESCRIPTION OF THE DRAWING The invention may take form in certain parts and arrangements of parts, a preferred embodiment of which will be described in detail in this specification and illustrated in the accompanying drawing which forms a part hereof.

FIG. 1 is an elevational view showing an induction heating apparatus having the improvements of the present invention incorporated therein and with portions in section for clarity of illustration;

FIG. 2 is a plan view looking generally in the direction of arrows 2-2 of FIG. 1;

FIG. 3 is an elevational view looking generally in the direction of arrows 33 of FIG. 2;

FIG. 4 is a cross-sectional elevational view looking generally in the direction of arrows 4-4 of FIG. 2; and

HG. 5 is a partial elevational view showing a different mounting arrangement for an air delivery means.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawing, wherein the showings are for purposes of illustrating a preferred embodiment of the invention only and not for purposes of limiting same, FiG. 1 shows an apparatus for inductively heating a workpiece A. In the arrangement shown, workpiece A comprises an axleshaft including an elongated generally cylindrical shaft portion having an outwardly extending generally circular flange 12 at one end thereof. Flange 12 has a surface 14 facing shaft portion 10 and connected thereto by a circumferential rounded fillet 16. Surface 14 of flange 12 also defines a workpiece surface for workpiece A and extends substantially perpendicular to the longitudinal axis of shaft portion 10.

A rotatable chuck B, which may take many forms and is not a part of the present invention, is provided for holding workpiece A on centering spindle 46.

It will be recognized that many different known arand moving chuck B. Chuck E is shown rotatably mounted in a bearing 76 on a laterally extending portion 78 of support member C. Support member C has a laterally extending upper arm 80 having a centering spindle 82 thereon engaging the opposite end of shaft portion 10. Support C includes a vertical arm portion 84 having a rack 86 formed thereon. A motor D is drivingly connected with gear E which is in turn drivingly engaged with rack 86. Motor D is controlled by suitable control P for selective rotation in opposite directions.

An inductor G is provided for inductively heating workpiece A. Inductor G may take many different forms and is shown as a tubular coil having an open center through which shaft portion 10 of workpiece A may extend. Inductor G is supported by mounting members H having holes 90 therethrough communicating with the hollow interior of inductor G. Mounting members H are connected to a source of water or other coolant fluid by conduits 92. Coolant fluid enters holes 90 in the direction indicated by arrows 94 and flows through the hollow interior of inductor G. A first outlet conduit 96 is connected by brazing or the like to the outer peripheral wall of inductor G in fluid communication with the hollow interior thereof. Another conduit 98 is connected to the peripheral wall of inductor G in fluid flow communication with the hollow interior thereof. Conduit 98 has its end portion 102 extending intothe hollow interior of inductor G to form a dam.

I Coolant flows through upper coil 104 of inductor G from hole 90 in mounting member H and exits through outlet conduit 96. Coolant flows through lower or terminal inductor coil 106 from hole 90 in the other mounting member H and exits through outlet conduit 98. End portion 102 of conduit 98 forming a dam within the hollow interior of inductor G is not a fluidtype seal and simply separates the upper and lower coil for maximum flow of fluid coolant through each individual coil, and out its respective outlet conduit 96 or 98. Inductor mounting members H are attached to a transformer I which is electrically connected to inductor G in a known manner.

In accordance with one arrangement, an air pump J is connected through conduit 112 with an accumulator K which in turn is connected through conduit 114 with pressure-regulating valve L. Valve L is connected through conduit 116 with a needle valve 117. Valve 117 is connected through conduit 118 to a pressure sensor M. Conduit 120 defines an air delivery means connected with sensor M and has an outlet opening 122 positioned closely adjacent inductor G. Outlet opening 122 is formed in a plug member 124 inserted into end portion 126 of air delivery conduit and secured therein. Plug member 124 and end portion 126 of air delivery conduit defining a nozzle having an outlet opening 122 positioned for directing an air jet toward surface 14 on flange 12 of workpiece A. In the preferred arrangement, outlet opening 122 has a terminal edge lying in a plane 128 which is substantially parallel to surface 14 of flange 12. The air jet is directed through opening 122 substantially perpendicular to surface 14.

Terminal coil 106 of inductor G is deformed into somewhat of an oval shape as shown in FIG. 4 so that it may be positioned closely adjacent surface 14 of flange 12 and fillet 16. Terminal coil 106 has a terminal surface 130 facing surface 14 and also lying substan tially in plane 128. It will be recognized that the relationship between terminal surface 130 and the terminal edge of outlet opening 122 may be varied so that they do not lie in a substantially common plane depending upon the application to which the device is put. It is merely sufficient that outlet opening 122 be positioned, and its back pressure measured, in accordance with a predetermined relationship for indicating the position of a workpiece surface relative to terminal surface 130 of terminal coil 106 on inductor G.

In one arrangement, a mounting bracket P has a lower inclined leg member 136 secured to the outer peripheral surface of terminal coil 106 as by brazing. Support bracket P includes an upper portion 138 having a notch 140 therein for receiving conduit 120. The outer peripheral surface of conduit 120 is brazed to the surfaces of mounting bracket P adjacent notch 140.

In accordance with a preferredarrangement, means are provided for cooling the terminal end portion or nozzle part of conduit 120. The peripheral wall of terminal coil 106 on inductor G has an opening 144 formed therein. At least a portion of end portion 126 of conduit 120 is received in opening 144 and projects into hollow interior 1480f terminal coil 106. End portion 126 of conduit 120 is brazed all around as at to seal opening 144 in terminal coil 106. With thisarrangement, the terminal end or nozzle portion of conduit 120 is also contracted by and cooled with fluid coolant circulating through the hollow interior of inductor G. I y

In operation of the device, a workpiece A is centered between spindles 46 and 82, and is mounted in chuck B with its upper end portion extending through inductor G. A control is then thrown to energize motor D for rotating pinion gear E to cooperate with rack 86 and move support C upwardly. This moves workpiece surface 14 toward inductor G. Pump .l is also operating so that a jet of air is being directed through outlet 122 toward surface 14. When surface 14 has reached a desirable position closely adjacent inductor G, back pressure will be created within conduit 120 and amplified within pressure amplifier M. The amplified pressure may be indicated by a gage 154 and may also be sent through line 156 to control F for stopping motor D and reversing its direction of rotation for driving support C downward through cooperation of pinion gear E and rack 86. Simultaneously with stopping of motor D, transformer I is energized for sending current to inductor G. Also simultaneously with stopping of motor D, a motor for rotatably driving chuck B is started. Workpiece A then rotates as it is being inductively heated and moves downwardly when motor D reverses direction. It will be recognized that inductor G may include an integral quench body for directing a quenching fluid onto workpiece A immediately below scanning inductor G.

With the arrangement described, surface 14 of workpiece A will be properly positioned closely adjacent inductor G for hardening fillet l6 regardless of the thickness of flange 12. In this operating arrangement of the device, a fixed limit switch 170 may be provided for cooperation with upper and lower stops 172 and 174 on arm 84 of support C. Upper limit stop 172 opens limit switch 170 when support C reaches its lowermost position to shut the motors and transformer off when workpiece A has been completely heat treated. Lower limit stop 174 may be provided as a safety precaution to stop the device in the event the air measuring and sensing device is malfunctioning. For example, if the air measuring and sensing device is not functioning, it will not stop and reverse operation of motor D. Therefore, chuck B will continue to move upwardly and cause extensive damage to inductor G. Limit switch 170 may be positioned just beyond the point where surface 14 should be stopped by the air measuring and sensing device to prevent extensive damage.

In an arrangement where the air measuring and sensing device simply measures the thickness of flange l2, limit switch 170 is positioned for being tripped by lower limit stop 174 to stop and reverse motor D when surface 14 is in a predetermined desired relationship closely adjacent inductor G. With this arrangement, limit switch 170 and stop 174 are adjusted so that device will properly operate over a range of predetermined tolerances for the thickness of flange 12. When the thickness of flange 12 is within the desirable tolerance, the back pressure sensed will be within a predetermined range of values. If the thickness of flange 12 is greater than the desirable tolerance, the back pressure sensed will be greater than the predetermined range and indicate that the workpiece should be ejected without heat treating. If flange 12 is thinner than the desirable tolerance, the sensed back pressure will be lower than the predetermined range of values and indicate that workpiece A should be ejected without heat treating.

It will be recognized that it is desirable to have outlet 122 stationarily fixed in position adjacent inductor G so that relative movement cannot occur between outlet 122 and inductor G during operation of the device. This is not to say that adjustability cannot be provided. For example, conduit 120 may be fastened as at 180 onto a horizontally extending plate member 182 in FIG. 5. Plate member 182 has an end portion 184 slidably received in a support member S for vertical movement. A screw 186 may be rotatably supported in suitable bearings provided in laterally extending legs 188 of support S. Screw 186 is threaded through a threaded opening 190 in plate member 182. Screw 186 is provided with hexagonal end portions 192. This provides an arrangement for supporting outlet 122 closely adjacent inductor G without being mounted directly thereto. This arrangement also provides for some vertical adjustment of the relative position of outlet 122 relative to inductor G in the direction of arrows 196. A slack flexible conduit portion 202 may be connected by couplings 204 with conduit for allowing slight vertical adjustment. Plate member 182 may also be formed in two overlapping portions adjustably secured together as by bolts extending through holes in one plate member and slots in the other plate member for slight adjustable movement horizontally as indicated by arrows 206. Thus, although it is possible to adjustably position outlet 122 adjacent inductor G, outlet 122 is still always fixed in a stationary position relative to inductor G so that outlet 122 and inductor G cannot move relative to one another during operation of the device.

The improved arrangement of the present invention has been described with reference to measuring a relative relationship between an inductor and a workpiece surface. As so used, the words relative relationship include indirect measurement of workpiece thickness as described in the specification.

Although the invention has been described with reference to a preferred embodiment, it is obvious that equivalent alterations and modifications will occur to others skilled in the art upon the reading and understanding of this specification. The present application includes all such equivalent alterations and modifications and is limited only by the scope of the claims.

Having thus described my invention, I claim:

1. In an induction heating device including inductor means for heating a workpiece having a surface facing said inductor means, the improvement comprising; measuring means for measuring a relative relationship between said inductor means and said surface, said measuring means including air delivery means having an outlet stationarily positioned adjacent said inductor means for directing an air jet toward said surface, and sensing means for sensing back pressure in said air delivery means to indicate existence of said relative relationship.

2. The device of claim 1 wherein said inductor means has a hollow interior and a peripheral wall and said air delivery means includes a nozzle having said outlet therein, said nozzle having at least a portion thereof projecting through said peripheral wall into said hollow interior, whereby fluid coolant circulated through said hollow interior contacts and cools said portion of said nozzle.

3. The device of claim 1 wherein said air delivery means includes a nozzle having said outlet therein and said nozzle is mounted on said inductor means.

4. The device of claim 1 wherein said inductor means includes a tubular coil having a terminal coil with a terminal surface facing said surface of said workpiece, and said outlet being positioned substantially in said plane.

5. The device of claim 1 wherein said outlet is positioned for directing said air jet substantially perpendicular to said surface.

6. The device of claim 1 wherein said inductor means defines a first structure and said workpiece defines a second structure, and said relative relationship between said inductor means and said surface of said workpiece comprises distance, at least one of said structures being movable toward and away from the other of said structures for bringing said inductor means and said surface into and out of a closely adjacent desirable predetermined distance relationship relative to one another, said sensing means being operative to indicate existence of said desirable predetermined distance relationship.

7. The device of claim 1 wherein said inductor means defines a first structure and said workpiece defines a second structure, and said relative relationship between said inductor means and said surface of said workpiece comprises distance, at least one of said structures being movable toward and away from the other of said structures for bringing said inductor means and said surface into and out of a closely adjacent desirable predetermined distance relationship relative to one another, said sensing means being operative to indicate existence of saiddesirable predetermined distance relationship by automatically stopping movement of said one structure toward said other structure when said predetermined desirable predetermined distance relationship is established.

8. The device of claim 1 wherein said workpiece includes a generally cylindrical shaft portion having an outwardly extending flange on one end portion thereof, said flange having a flange surface facing said shaft portion, said flange surface defining said workpiece surface facing said inductor means.

9. The device of claim 8 wherein said inductor means defines a first structure and said workpiece defines a second structure, and said relative relationship between said inductor means and said flange surface comprises distance, at least one of said structures being movable toward and away from the other of said structures for bringing said inductor means and said flange surface into and out of a closely adjacent desirable predetermined distance relationship relative to one another, said sensing means being operative to indicate existence of said desirable predetermined distance relationship.

10. A method of inductively heating workpieces comprising the steps of; moving a workpiece surface and an inductor toward one another, directing an air jet toward said workpiece surface from an air delivery means having an outlet fixedly positioned adjacent said inductor, and sensing back pressure in said air delivery means to indicate existence of a desirable relative relationship between said inductor and workpiece surface.

11. The method of claim 10 wherein said inductor has a hollow interior and a peripheral wall, said air delivery means including a nozzle having said outlet therein, said nozzle having at least a portion thereof projecting through said wall into said hollow interior, and further including the step of circulating fluid coolant through said hollow interior for cooling said inductor and said nozzle.

12. The method of claim 10 wherein said desirable relative relationship between said inductor and said surface comprises closely adjacent desirable predetermined distance relationship, and said step of sensing and indicating being carried out by automatically stopping movement of said inductor and workpiece surface toward one another when said predetermined distance relationship is established.

13. A method of inductively heating an axleshaft or the like having a generally cylindrical shaft portion and an outwardly extending flange on one end portion thereof, said flange having a flange surface facing said shaft portion, comprising the steps of; positioning said shaft portion through the open center of an induction coil, relatively moving said coil and said flange toward one another, directing an air jet toward said flange surface from an air delivery means having an outlet fixedly positioned adjacent said inductor, and sensing back pressure in said air delivery means to indicate existence of a desirable relative relationship between said inductor and said flange surface. 

1. In an induction heating device including inductor means for heating a workpiece having a surface facing said inductor means, the improvement comprising; measuring means for measuring a relative relationship between said inductor means and said surface, said measuring means including air delivery means having an outlet stationarily positioned adjacent said inductor means for directinG an air jet toward said surface, and sensing means for sensing back pressure in said air delivery means to indicate existence of said relative relationship.
 2. The device of claim 1 wherein said inductor means has a hollow interior and a peripheral wall and said air delivery means includes a nozzle having said outlet therein, said nozzle having at least a portion thereof projecting through said peripheral wall into said hollow interior, whereby fluid coolant circulated through said hollow interior contacts and cools said portion of said nozzle.
 3. The device of claim 1 wherein said air delivery means includes a nozzle having said outlet therein and said nozzle is mounted on said inductor means.
 4. The device of claim 1 wherein said inductor means includes a tubular coil having a terminal coil with a terminal surface facing said surface of said workpiece, and said outlet being positioned substantially in said plane.
 5. The device of claim 1 wherein said outlet is positioned for directing said air jet substantially perpendicular to said surface.
 6. The device of claim 1 wherein said inductor means defines a first structure and said workpiece defines a second structure, and said relative relationship between said inductor means and said surface of said workpiece comprises distance, at least one of said structures being movable toward and away from the other of said structures for bringing said inductor means and said surface into and out of a closely adjacent desirable predetermined distance relationship relative to one another, said sensing means being operative to indicate existence of said desirable predetermined distance relationship.
 7. The device of claim 1 wherein said inductor means defines a first structure and said workpiece defines a second structure, and said relative relationship between said inductor means and said surface of said workpiece comprises distance, at least one of said structures being movable toward and away from the other of said structures for bringing said inductor means and said surface into and out of a closely adjacent desirable predetermined distance relationship relative to one another, said sensing means being operative to indicate existence of said desirable predetermined distance relationship by automatically stopping movement of said one structure toward said other structure when said predetermined desirable predetermined distance relationship is established.
 8. The device of claim 1 wherein said workpiece includes a generally cylindrical shaft portion having an outwardly extending flange on one end portion thereof, said flange having a flange surface facing said shaft portion, said flange surface defining said workpiece surface facing said inductor means.
 9. The device of claim 8 wherein said inductor means defines a first structure and said workpiece defines a second structure, and said relative relationship between said inductor means and said flange surface comprises distance, at least one of said structures being movable toward and away from the other of said structures for bringing said inductor means and said flange surface into and out of a closely adjacent desirable predetermined distance relationship relative to one another, said sensing means being operative to indicate existence of said desirable predetermined distance relationship.
 10. A method of inductively heating workpieces comprising the steps of; moving a workpiece surface and an inductor toward one another, directing an air jet toward said workpiece surface from an air delivery means having an outlet fixedly positioned adjacent said inductor, and sensing back pressure in said air delivery means to indicate existence of a desirable relative relationship between said inductor and workpiece surface.
 11. The method of claim 10 wherein said inductor has a hollow interior and a peripheral wall, said air delivery means including a nozzle having said outlet therein, said nozzle having at least a portion thereof projecting through said wall into saId hollow interior, and further including the step of circulating fluid coolant through said hollow interior for cooling said inductor and said nozzle.
 12. The method of claim 10 wherein said desirable relative relationship between said inductor and said surface comprises closely adjacent desirable predetermined distance relationship, and said step of sensing and indicating being carried out by automatically stopping movement of said inductor and workpiece surface toward one another when said predetermined distance relationship is established.
 13. A method of inductively heating an axleshaft or the like having a generally cylindrical shaft portion and an outwardly extending flange on one end portion thereof, said flange having a flange surface facing said shaft portion, comprising the steps of; positioning said shaft portion through the open center of an induction coil, relatively moving said coil and said flange toward one another, directing an air jet toward said flange surface from an air delivery means having an outlet fixedly positioned adjacent said inductor, and sensing back pressure in said air delivery means to indicate existence of a desirable relative relationship between said inductor and said flange surface. 